A191613 Number of even divisors of lambda(n).

0, 0, 1, 1, 2, 1, 2, 1, 2, 2, 2, 1, 4, 2, 2, 2, 4, 2, 3, 2, 2, 2, 2, 1, 4, 4, 3, 2, 4, 2, 4, 3, 2, 4, 4, 2, 6, 3, 4, 2, 6, 2, 4, 2, 4, 2, 2, 2, 4, 4, 4, 4, 4, 3, 4, 2, 3, 4, 2, 2, 8, 4, 2, 4, 4, 2, 4, 4, 2, 4, 4, 2, 9, 6, 4, 3, 4, 4, 4, 2, 4, 6, 2, 2, 4, 4, 4, 2, 6, 4, 4, 2, 4, 2, 6, 3, 10, 4, 4, 4, 6, 4, 4, 4, 4

Offset

1,5

Comments

Lambda is the function in A002322.

Links

Antti Karttunen, Table of n, a(n) for n = 1..16384

Formula

a(n) = A183063(A002322(n)). - Michel Marcus, Mar 18 2016

Example

a(13) = 4 because lambda(13) = 12 and the 4 even divisors are { 2, 4, 6, 12}.

Mathematica

f[n_] := Block[{d = Divisors[CarmichaelLambda[n]]}, Count[EvenQ[d], True]]; Table[f[n], {n, 80}]
(* Second program: *)
Array[DivisorSum[CarmichaelLambda@ #, 1 &, EvenQ] &, 105] (* Michael De Vlieger, Dec 04 2017 *)

Prog

(PARI) a(n) = sumdiv(lcm(znstar(n)[2]), d, 1-(d%2)); \\ Michel Marcus, Mar 18 2016

Crossrefs

Cf. A002322, A183063, A193322, A193386.

Sequence in context: A324888 A249145 A048684 * A298642 A243404 A219181

Adjacent sequences: A191610 A191611 A191612 * A191614 A191615 A191616

Keyword

nonn

Author

Michel Lagneau, Jul 22 2011

Extensions

More terms from Antti Karttunen, Dec 04 2017

Status

approved